Originally published on Apr 17, 2024
Building Overview
Name: Nakanoshima Festival Tower
Owner: The Asahi Shimbun Company
Design and Supervision: Nikken Sekkei Ltd.
Construction: Takenaka Corporation
Location: 2-22 Nakanoshima, Kita-ku, Osaka
Purpose: Office, theater, shops, etc.
Site Area: Approximately 8,150 square meters
Building Area: Approximately 5,700 square meters
Total Floor Area: Approximately 146,000 square meters
Floors: 39 above ground, 3 below ground
Height: Approximately 200 meters
Foundation Depth: 16.5 meters below ground
Intermediate Seismic Isolation Structure We adopted an intermediate seismic isolation structure, using seismic rubber and hydraulic dampers above the concert hall. It can withstand earthquakes 1.5 times the intensity of the Great Hanshin Earthquake, with high seismic resistance, considering the Uemachi fault line type earthquake.
Effective Absorption of Seismic Energy The seismic isolation layer is equipped with lead-filled laminated rubber with a maximum angle of 1.5 meters. Additionally, hydraulic dampers work together to absorb the seismic energy, responding to expected long-period seismic movements like the Tokai and Tonankai earthquakes, enhancing seismic performance while improving office living quality.
Foundation Piles Reach 86 Meters Underground The foundation piles supporting the building extend to 86 meters underground. This support layer, over 80 meters, is rare in other high-rise buildings. Large beams are also used to support office floors.
The twin towers of Nakanoshima Festival Tower have unique structures, achieving the highest level of seismic performance domestically. During a magnitude 7 earthquake similar to the Great Hanshin Earthquake, the primary functions of both towers can be maintained, receiving the highest S-class rating. They can also withstand long-period seismic movements like the Nankai Trough megaquake.
Since the concert hall and office floors are separate, the "intermediate seismic isolation" structure (seismic isolation 1) was adopted. Seismic rubber was installed on top of the concert hall to reduce the shaking of the upper floors. The West Tower, with its slender steel frame structure, adopted "super damping" (damping 2). High damping force dampers were installed in the lower floors, where seismic forces are concentrated, to absorb the vibrations.
The design goal of the intermediate seismic isolation structure is to maintain minor structural damage and ensure main functions after a major earthquake. Considering the concert hall on the lower floors and the office on the upper floors, and their structural differences, we adopted the intermediate seismic isolation structure to meet the seismic design goals. The seismic isolation layer is set at a height of 44.9 meters above ground, with the stage tower on the east side two floors higher (53.7 meters above ground), forming different height seismic isolation layers. The seismic isolation materials consist of lead-filled laminated rubber isolators (LRB) and hydraulic dampers. The LRBs, sized at 1500mm angles, are installed in sets of 32, supporting approximately 95% of the weight above the seismic isolation layer. Hydraulic dampers are installed in the X and Y directions, with a total of 24, having overflow loads and maximum loads of 800kN and 1000kN. The total yield shear of the lead plugs and hydraulic dampers accounts for about 4.5% of the weight above the seismic isolation layer. The LRBs and hydraulic dampers are placed parallel to the main columns to reduce eccentricity and torsional effects, maintaining balance.
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